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In the present article, a double power series analytical layerwise model is proposed for analysis of multilayer orthotropic plates with arbitrary shapes of interfacial bond defects. In contrast to the previous models, the discontinuity in the lateral deflections of the successive layers is also considered. The adhesive bonding layers are modeled by elastic elements with normal and shear stiffness coefficients; so that, the continuity conditions of the transverse shear and normal stresses are met at the layer interfaces. It is the first time that an analytical solution rather than the data-dependent finite element method is proposed for stress and displacement analysis of multilayer rectangular plates with arbitrary shapes of interfacial bond damages, including the discontinuity in the transverse displacements of the successive layers. Results of the transverse displacement and stresses are then refined according to the 3D theory of elasticity. Results reveal that even small violations in the bonding between layers, may increase the resulting stresses, lateral deflections, and the differences between lateral deflections of the successive layers to more than twice, thrice, and five times, respectively. Moreover, in contrast to the growth of the in-plane stresses, redistribution of the transverse shear stress is governed by the equilibrium rather than the constitutive-law-based conditions. [ABSTRACT FROM AUTHOR]

By using a three-dimensional (3D) space-frame-like model, a molecular mechanics (MM) approach is proposed for determination of the buckling loads, effective Young's modulus and Poisson's ratio of the nanosheets, using a proper unit cell. The governing equations are derived based on the 3D kinematics of deformations and the principle of minimum total potential energy. The unit-cell-based results are employed for the space-frame-like finite element model of the nanosheet. The nonlinear MM equations are solved by representing bonds of the boron nitride nanosheet (BNNS) by beam elements to extract the local characteristics. These properties are employed in modelling of the nanosheet, as a space-frame-like finite element structure. The force field constants are chosen according to the Morse, AMBER, UFF and DREIDING models to determine the buckling strength, and effective Poisson's ratio and in-plane rigidity of the whole graphene and BNNSs. Silicon Carbide nanosheets are analysed based on different force constants. These results are concordant with the results available in the literature. The comparisons reveal that the DREIDING force field usually gives the most accurate predictions. [ABSTRACT FROM AUTHOR]

Based on the three-dimensional theory of elasticity, a comprehensive stress analysis is performed for the rotating bidirectional functionally graded thick axisymmetric circular/annular plates, for the first time. The plate may be subjected to arbitrary distributions of the transverse load and various mixed (Dirichlet-type and Neumann-type) edge conditions. Furthermore, the circular plate may be supported by a nonuniform elastic foundation or a rigid substrate. In contrast to the very limited works presented for the rotating functionally graded circular plates so far, the transverse flexibility and the transverse stress components are considered and studied in the present research. Since finite element and boundary element techniques, due to their integral natures, cannot adequately trace abrupt changes of the quantities, a second-order point collocation method with forward–backward schemes is adopted to solve the system of the governing and boundary conditions. Effects of the distributions of the various material properties (Poisson’s ratio, Young’s modulus, and mass density), angular velocity, foundation compliance, and edge conditions are evaluated. Results reveal that radially graded or transversely graded material properties significantly affect distribution and magnitude and location of the extrema of the stress components and the lateral deflections and orientation of the general neutral surface of the plate. [ABSTRACT FROM AUTHOR]

Abstract: Three-dimensional buckling analysis of the functionally graded plates has not been investigated under non-uniform in-plane compressive loads so far. The only available work in this field has been performed based on the first-order shear deformation theory, employing the simple rule of mixtures. In the present paper, a non-linear three-dimensional energy-based elasticity analysis is developed for buckling investigation of functionally graded plates subjected to non-uniform in-plane compressions. The comparative studies performed in the present paper reveal that the rule of mixtures is generally inappropriate for determination of the effective material properties. For this reason, a micromechanics-based model is used instead. In contrast to the common displacement-based numerical or semi-analytical elasticity analyses (with C 0-continuity), present formulations are C 2-continuous due to using the proposed 3D cubic B-spline element. Buckling analysis is accomplished through a two-step procedure wherein the prebuckling stresses are determined first. A non-linear weighted-residuals-based finite element solution is used. The buckling load associated with each of the adopted 8 types of the load distribution patterns is detected based on a generalized geometric stiffness concept. Various and comprehensive parametric studies are accomplished and various boundary conditions are considered to extract more precise conclusions. [Copyright &y& Elsevier]

Abstract: In the present paper, a three-dimensional elasticity approach is employed to investigate buckling of heterogeneous functionally graded plates under biaxial compression, shear, tension-compression, and shear-compression load conditions. In this regard, a formulation that employs a full compatible three-dimensional Hermitian element with 168 degrees of freedom and guarantees continuity of the strain and stress components is used. It is known that all of the available famous commercial finite element softwares and the proposed series solutions satisfy continuity conditions of the displacement rather than the stress components. Buckling occurrence is detected based on checking both the instability onset and equilibrium criteria. Results are extracted based on a Galerkin-type orthogonality. Therefore, they are more accurate than those obtained based on the traditional Ritz method. The presented three-dimensional finite element analysis and the extracted results are quite new. A vast variety of results including results of biaxial compression, compression-tension, shear, and shear-compression load cases is considered and discussed in detail. [Copyright &y& Elsevier]

Three-dimensional bending and stress analyses of the rotating two-directional functionally graded annular/circular plates or disks have not been accomplished so far. This task is performed in the present paper, employing a finite element formulation with a C1- continuity. Therefore, both transversely graded and radially-graded plates may be analyzed as special cases of the present research. Distribution of the transverse loads as well as coefficients of the elastic foundation may be non-uniform. Mixed stress-based and displacement-based edge conditions are considered to cover many practical applications. Compatible Hermitian elements are employed to develop a consistent formulation and avoid jumps in the stress components at the elements interfaces. In contrast to the very limited works presented for the rotating functionally graded circular plates so far, the transverse flexibility and the transverse stress components are also considered in the present research. Finally, influences of the material properties distribution, angular speed, geometric parameters, and the elastic foundation on distributions of the stress and displacement components are investigated for a variety of edge and boundary conditions and some design criteria are extracted. [ABSTRACT FROM AUTHOR]

Abstract: Buckling analysis of the functionally graded viscoelastic circular plates has not been carried out so far. In the present paper, a series solution is developed for buckling analysis of radially graded FG viscoelastic circular plates with variable thickness resting on two-parameter elastic foundations, based on Mindlin''s plate theory. The complex modulus approach in combination with the elastic–viscoelastic correspondence principle is employed to obtain the solution for various edge conditions. A comprehensive sensitivity analysis is carried out to evaluate effects of various parameters on the buckling load. Results reveal that the viscoelastic behavior of the materials may postpone the buckling occurrence and the stiffness reduction due to the section variations may be compensated by the graded material properties. [Copyright &y& Elsevier]

Abstract: Almost no dynamic buckling analysis has been performed so far for the sandwich/multilayer viscoelastic shells. Even the vibration analyses of the mentioned shells have been restricted to the harmonic loads ignoring the transverse stresses and their continuity at the mutual interfaces of the layers, and the transverse flexibility of the shell. In the present paper, a high-order double-superposition global–local theory inherently suitable for nonlinear analyses is proposed and employed for nonlinear dynamic buckling and postbuckling analyses of imperfect viscoelastic composite/sandwich cylindrical shells subjected to thermomechanical loads. Depending on the nature of the applied loads, both complex modulus and hierarchical constitutive models are used for the viscoelastic materials. Results reveal that as the time duration of the suddenly applied loads decreases beyond the first natural period of the shell, the dynamic buckling load becomes much higher than the static buckling load, especially for the rectangular load–time histories. Furthermore, the relaxation behavior of the viscoelastic material may decrease the dynamic buckling load. [Copyright &y& Elsevier]

higher-order global-local theory is proposed based on the double-superposition concept for free vibration and dynamic buckling analyses of viscoelastic composite/sandwich plates subjected to thermomechanical loads. In contrast to all theories proposed so far for analysis of the viscoelastic plates, the continuity conditions of the transverse shear and normal stresses at the layer interfaces and the nonzero traction conditions at the top and bottom surfaces of the sandwich plates are satisfied. Another novelty is that these conditions may be satisfied for viscoelastic plates with temperature-dependent material properties and nonlinear behaviors subjected to thermomechanical loads. Furthermore, transverse flexibility is also taken into account. Some dynamic buckling/wrinkling analyses of the viscoelastic plates are performed in the present paper, for the first time. Comparisons made between results of the paper and results reported by well-known references confirm the accuracy and the efficiency of the proposed theory and the relevant solution algorithm. [ABSTRACT FROM AUTHOR]

Based on the idea of double superposition, an accurate high-order global–local theoryis proposed for bending and vibration analysis of cylindrical shells subjected to thermo-mechanical loads, for the first time. The theory has many novelties, among them: (1) less computational time due to the use of the global–local technique and matrix formulations; (2) satisfaction of the complete kinematic and transverse stress continuity conditions at the layer interfaces under thermo-mechanical loads; (3) consideration of the transverse flexibility; (4) release of Love–Timoshenko assumption; and (5) capability of investigating the local phenomena. Various comparative examples are included to validate the theory and to examine its accuracy and efficiency. [ABSTRACT FROM AUTHOR]

Abstract: In the present paper, analytical and numerical elastodynamic solutions are developed for long thick-walled functionally graded cylinders subjected to arbitrary dynamic and shock pressures. Both transient dynamic response and elastic wave propagation characteristics are studied in these non-homogeneous structures. Variations of the material properties across the thickness are described according to both polynomial and power law functions. A numerically consistent transfinite element formulation is presented for both functions whereas the exact solution is presented for the power law function. The FGM cylinder is not divided into isotropic sub-cylinders. An approach associated with dividing the dynamic radial displacement expression into quasi-static and dynamic parts and expansion of the transient wave functions in terms of a series of the eigenfunctions is employed to propose the exact solution. Results are obtained for various exponents of the functions of the material properties distributions, various radius ratios, and various dynamic and shock loads. [Copyright &y& Elsevier]

Abstract: The available accurate shell theories satisfy the interlaminar transverse stress continuity conditions based on linear strain–displacement relations. Furthermore, in majority of these theories, either influence of the transverse normal stress and strain or the transverse flexibility of the shell has been ignored. These effects remarkably influence the non-linear behavior of the shells especially in the postbuckling region. Furthermore, majority of the buckling analyses performed so far for the laminated composite and sandwich shells have been restricted to linear, static analysis of the perfect shells. Moreover, almost all the available shell theories have employed the Love–Timoshenko assumption, which may lead to remarkable errors for thick and relatively thick shells. In the present paper, a novel three-dimensional high-order global-local theory that satisfies all the kinematic and the interlaminar stress continuity conditions at the layer interfaces is developed for imperfect cylindrical shells subjected to thermo-mechanical loads. In comparison with the layerwise, mixed, and available global-local theories, the present theory has the advantages of: (1) suitability for non-linear analyses, (2) higher accuracy due to satisfying the complete interlaminar kinematic and transverse stress continuity conditions, considering the transverse flexibility, and releasing the Love–Timoshenko assumption, (3) less required computational time due to using the global-local technique and matrix formulations, and (4) capability of investigating the local phenomena. To enhance the accuracy of the results, compatible Hermitian quadrilateral elements are employed. The buckling loads are determined based on a criterion previously published by the author. [ABSTRACT FROM AUTHOR]

Abstract: Nonlinear transient thermal stress and elastic wave propagation analyses are developed for hollow thick temperature-dependent FGM cylinders subjected to dynamic thermomechanical loads. Stress wave propagation, wave shape distortion, and speed variation under impulsive mechanical loads in thermal environments are also investigated. In contrast to researches accomplished so far, a second-order formulation rather than a first-order one is employed to improve the accuracy. The FDM method (as a point-collocation FEM method) is used. It is known that other FEM methods cannot show the actual trend jumps due to distributing the abrupt changes in the quantities as the numerical errors and the residuals of the governing equations among the nodal results. Furthermore, the required computational time and allocated computer memory are much reduced by the present solution algorithm. The cylinder is not divided into isotropic sub-cylinders. Therefore, artificial wave reflections from the hard interfaces are avoided. Time variations of the temperatures, displacements, and stresses due to the dynamic or impulsive loads are determined by solving the resulted highly nonlinear governing equations using an iterative updating solution scheme. A sensitivity analysis includes effects of the volume fraction indices, dimensions, and temperature-dependency of the material properties is performed. Results reveal the significant effect of the temperature-dependency of the material properties on the thermoelastic stresses and present some interesting characteristics of the thermoelastic and wave propagation behaviors. [Copyright &y& Elsevier]

Abstract: The available plate theories have been generally calibrated using linear strain–displacement expressions. Furthermore, many of them do not consider the transverse normal stress continuity and the transverse flexibility of the sandwich plates. Majority of the investigations performed so far in the buckling analysis of the sandwich plates, have been restricted to linear buckling analysis of the perfect sandwich plates based on theories that either violate the continuity condition of the transverse stresses at the layer interfaces or do not satisfy the mentioned condition when nonlinear strain–displacement expressions are used. Therefore, their results may be unreliable for nonlinear stress and buckling (especially in the postbuckling region) analyses. In the present paper, nonlinear strain–displacement expressions are employed for imperfect sandwich plates subjected to thermo-mechanical loads to propose an accurate global–local theory that satisfies the continuity of all of the transverse stress components. The theory is presented in a compact matrix form. Compatible Hermitian elements with C1 continuity are employed to enhance the results. Buckling and wrinkling loads are detected employing a criterion previously published by the author. Comparisons made in the paper with results reported by well-known references, confirm the accuracy and the efficiency of the proposed theory and the relevant solution algorithm. [Copyright &y& Elsevier]

Abstract: The available plate theories either have not considered the interlaminar stress continuity condition or have been calibrated based on linear strain–displacement relations. Moreover, almost all buckling analyses performed so far employing the global–local plate theories, were restricted to linear, static buckling analyses of the perfect plates, neglecting the transverse normal strain and stress. Researches available in literature for dynamic buckling analyses of the sandwich plates are very rare. In the present paper, a generalized high-order global–local theory that satisfies all the kinematic and transverse stress continuity conditions at the interfaces of the layers, is proposed to investigate dynamic buckling of imperfect sandwich plates subjected to thermo-mechanical loads. In comparison to the layerwise, mixed, and available global–local theories, the present theory has the advantages of: (1) less required computational time due to using the global–local technique and matrix formulations, (2) higher accuracy due to satisfying the complete interlaminar kinematic and transverse stress continuity conditions and considering the transverse flexibility, (3) suitability for non-linear analyses, (4) capability of investigating the local phenomena, such as the wrinkling. To enhance the accuracy of the results, compatible Hermitian quadrilateral elements are employed. The buckling loads are determined based on a criterion previously published by the author. [Copyright &y& Elsevier]

Abstract: Dynamic buckling analysis of FGM plates has not been accomplished so far. In the present paper, vibration and dynamic buckling of FGM rectangular plates with surface-bonded or embedded piezoelectric sensors and actuators subjected to thermo-electro-mechanical loading conditions are investigated. A finite element formulation based on a higher-order shear deformation theory is developed. Both initial geometric imperfections of the plate and temperature-dependency of the material properties are taken into account. Dynamic buckling of plates already pre-stressed by other forms of loading conditions is assumed to occur under suddenly applied thermal or mechanical loads. A nine-node second order Lagrangian element, an efficient numerical algorithm for solving the resulted highly non-linear governing equations, and an instability criterion already proposed by the author are employed. A simple negative velocity feedback control is used to actively control the dynamic response of the plate. Results show that generally, initial geometric imperfections lead to an increased fundamental bending natural frequency and decreased buckling loads. Furthermore, buckling mitigation due to utilizing integrated piezoelectric sensors and actuators is mainly achieved in extremely high gain values. Therefore, the piezoelectricity effect on the buckling load is small in applicable voltages. It is also noticed that the temperature-dependency and initial geometric imperfections remarkably affect the buckling loads. [Copyright &y& Elsevier]

Abstract: Dynamic buckling of piezolaminated plates under thermo-electro-mechanical loads has not been investigated so far. In the present paper, effects of the thermo-piezoelasticity on the dynamic buckling under suddenly applied thermal and mechanical loads are investigated for imperfect rectangular composite plates with surface-bonded or embedded piezoelectric sensors and actuators. A finite element formulation based on a higher-order shear deformation theory is developed. Both the initial geometric imperfections of the plate and the temperature-dependency of the material properties are taken into account. Complex dynamic loading combinations include in-plane mechanical loads, heating, and electrical actuations are considered. A nine-node second order Lagrangian element, an efficient numerical algorithm for solving the resulted highly nonlinear governing equations, and an instability criterion already proposed by the author are employed. A simple negative proportional feedback control is used to actively control the transient response of the plate. Results show that buckling mitigation due to utilizing integrated piezoelectric sensors and actuators is mainly achieved in extremely high gain values. It is also noticed that in many cases, effects of the control voltage on the results may be ignored compared to the temperature-dependency of the material properties and initial geometric imperfections effects. [Copyright &y& Elsevier]

In this study, effects of the presence of vacancy defects in a hexagonal nanosheet on Young's modulus, effective Poisson's ratio, buckling loads and buckling modes, regardless of its constituent atoms, have been studied. Explicit expressions are proposed in order to define these characteristics considering a defect distribution term as a modifying parameter. Molecular structural mechanics concepts and FEM simulation are utilized in order to obtain these expressions and results. Different sizes and shapes of defects as well as random distribution of vacancies have been considered. The results for perfect Boron Nitride, Silicon Carbide and graphene nanosheet as well as defected Boron Nitride nanosheets are in a good agreement with those available in literature. Linear degradation behavior of Young's modulus and linear increase of effective Poisson's ratio in terms of defects distribution are observed in obtained results. A second order behavior is also observed in decreasing buckling load in terms of increasing vacancy distribution. Moreover, buckling mode characteristics due to the percentage of defects distribution has been investigated. [ABSTRACT FROM AUTHOR]